1. The Field of the Invention
The present invention generally relates to electronic and optical components. In particular, the present invention relates to a method for selectively modifying specified bulk properties of electronic and optical components, such as are found in integrated circuits and the like.
2. Related Technology
The importance of integrated circuits and the products made therefrom cannot be underestimated. Innumerable products featuring electronic components have been incorporated into nearly every facet of modern living. Such electronic products commonly include an integrated circuit (“IC”), which typically comprises a large number of miniaturized electronic components that are mounted on a printed circuit board (“PCB”), in order to provide the needed electronic functionality of the product.
During IC manufacture, much care is taken by the manufacturer to ensure that the various electronic components that comprise the IC possess operating characteristics that fall within an acceptable specification range. For instance, a resistor should possess a resistance that conforms to a desired specification. Such resistors are typically manufactured as “thin film” or “thick film” components on the PCB. In an untrimmed state, these resistors have tolerances in the range of a few percent for thin film and 5% to 15% for thick film.
If the IC component as manufactured does not possess the proper characteristics, it may be possible to modify, or tune, its operating characteristics. “Tuning” is generally referred to as the process by which one or more operating characteristics of an electronic component, such as an IC resistor, is modified. In resistors and other IC components, tuning is often accomplished by a method known as “trimming.” Known trimming techniques alter the resistive properties of the resistor, for instance, by removing resistor material therefrom. This removal is typically accomplished by mechanical ablation of a portion of the resistor by a laser device.
Despite its usefulness, several drawbacks exist with known laser trimming techniques. For example, the material removed from the resistor creates residue, which must be removed from the surface of the PCB after trimming, so as to avoid contamination thereof. This may often require an extra cleaning step during the manufacture of the PCB. Because it is a mechanical process, laser trimming is often limited to the top layer of a multi-layer PCB. Also, the nature of the resistor after treatment with known laser trimming techniques may cause undesired signal reflections from the resistor, as well as electromagnetic interference (“EMI”) from the resistor, during operation of the IC. Further, mechanical laser trimming often requires the use of select-on-test procedures for evaluating the success of the trimming procedure. Select-on-test evaluation is an expensive and slow process, which undesirably increases the time of manufacture for each PCB. As an alternative to mechanical laser trimming, other tuning techniques, such as thermal or electrical tuning, may be used to modify the bulk properties of electronic components. However, these techniques may also be either undesirable or unavailable depending on the type of PCB because of the risk of thermal or electrical damage to sensitive IC components.
A need therefore exists for a method of modifying the bulk properties of electronic components such as IC resistors without also creating the need for subsequent cleaning operations. A corresponding need also exists for a tuning method that reduces the chances for signal reflection and EMI during operation of the IC. Such a method should also provide for dynamic or active tuning of the electronic component, thus avoiding slower select-on-test circuit evaluation procedures that result in added fabrication/calibration expense. This method would desirably be used to tune components within single or multiple layer PCB structures, as well as non-IC electronic components. Finally, a need exists for a method that also allows for the modification of the bulk properties of optical components as well.